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Clinical Cancer Research Vol. 5, 521-524, March 1999
© 1999 American Association for Cancer Research

Clinical Trials

Leukocyte O6-Alkylguanine-DNA Alkyltransferase from Human Donors Is Uniformly Sensitive to O6-Benzylguanine1

Stanton L. Gerson2, Jane Schupp, Lili Liu, Anthony E. Pegg and Sankar Srinivasen

Division of Hematology/Oncology and the Ireland Cancer Center at Case Western Reserve University and University Hospital of Cleveland, Cleveland, Ohio 44106 [S. L. G., J. S., L. L., S. S.], and Department of Physiology, Pennsylvania State University School of Medicine, Hershey, Pennsylvania 17033 [A. E. P.]


   ABSTRACT
Top
 ABSTRACT
INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
O6-Alkylguanine-DNA alkyltransferase (AGT) is the key DNA repair protein responsible for resistance to chloroethylating and methylating agents that attack at the O6 position of guanine. O6-Benzylguanine (BG), a potent inhibitor of AGT, has recently entered clinical trials. A number of point mutations and at least one human polymorphism within AGT are associated with AGT resistance to inactivation by BG. In this study, we evaluated AGT inhibition by BG in an in vitro assay of peripheral blood mononuclear cell AGT from 56 normal donors, 42 Caucasians, and 14 Japanese. AGT activity ranged from 2.7 to 21.9 fmol/µg DNA and was similar in Japanese and Caucasian donors. Depletion of AGT by BG was uniform in all donors with mean ED50s of 0.37 µM BG in Caucasians and 0.36 µM BG in Japanese. To determine whether the gly160arg AGT polymorphism described in the Japanese population, and recently shown to be BG resistant, could be detected by this assay, we mixed purified gly160arg AGT protein with blood mononuclear cell extract and measured in vitro BG inactivation. The ED50 for the mixture of the gly160arg AGT and mononuclear cell extract was 9 µM BG. On the basis of results in 56 donors, we conclude that BG-resistant AGT, defined as an ED50 in mononuclear cells of >1 µM BG, is present in 0 of 56 donors, (95% confidence interval, 0–6%), suggesting that polymorphisms producing AGT-resistant BG are unusual in humans.


   INTRODUCTION
Top
 ABSTRACT
 INTRODUCTION
MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
The DNA repair protein AGT3 is the key protein responsible for repair of chemotherapy and carcinogen-induced DNA adducts at the O6 position of guanine (1) . High levels of AGT correlate with resistance to a number of chemotherapy agents, including BCNU, dacarbazine, procarbazine, streptozotocin, and temozolomide (1, 2, 3) , protect against the carcinogenic effects of methylating agents in animal models (4) . Low levels of AGT predict sensitivity to these agents (5) . Recently, a new therapeutic inhibitor of AGT, BG, has been described. BG sensitizes AGT expressing, BCNU-resistant tumors both in vitro and in xenograft models and is nontoxic at therapeutic concentrations (6 , 7) . Ongoing clinical trials have shown that it is possible to completely inhibit human AGT in patient peripheral blood mononuclear cells (8) and in tumors (9) . We have documented, using sequential deep tissue tumor biopsies, 100% depletion of human tumor AGT at doses of 120 mg/m2 BG, which produced maximum serum concentrations of 15 µM BG.

The wild-type AGT is remarkably sensitive to inhibition by BG, with an ED50 of about 0.5 µM in cell extracts (10) . However, mutations in certain regions of AGT confer resistance to BG. For instance, the bacterial AGT protein derived from the ada gene (11) , is remarkably resistant to BG but has similar capacity to remove O6-mG adducts compared with that of human AGT (12) . By point-directed mutagenesis, a number of amino acids that differ between ada and the human AGT gene, MGMT, when introduced into MGMT result in resistance to BG (13, 14, 15) . Some mutant AGTs have reduced reactivity with O6-mG or are unstable (15) . The recent description of a polymorphism in the Japanese population at codon 160 of MGMT, a glycine to arginine mutation, gly160arg, (16) , and the verification that this polymorphism resulted in a 20-fold increase in the ED50 for BG (17) raised concerns that polymorphisms in MGMT may be common and if present, could result in partial resistance to BG, which could impact significantly on clinical efficacy of BG as a modulator of AGT.


   MATERIALS AND METHODS
Top
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
RESULTS
 DISCUSSION
 REFERENCES
 
Heparinized blood was collected after informed consent from normal volunteer Caucasian and Japanese donors. The mononuclear layer from 40 ml of blood was obtained after Ficoll-Hypaque isopyknic gradient and processed for alkyltransferase (AGT) activity as described previously (18 , 19) .

This laboratory has reported lymphocyte AGT from normal donors since 1985 and has developed a method to standardize activity measurements over many years that allows us to relate measurements performed in 1985 (18) with those performed in 1998 (20–22). Key components of this standardization procedure include a single method of measurement using direct assay of residual O6-mG adducts on a substrate DNA, standardization of the substrate made from [3H]MNU-treated calf thymus DNA with direct comparison between old and new substrates, and use of AGT enzyme standards with each assay that have been from the same source over the entire time period.


   RESULTS
Top
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
DISCUSSION
 REFERENCES
 
In this study population of 56 donors, baseline peripheral blood mononuclear cell AGT varied 10-fold, from 2.7 to 21.9 fmol/µg DNA. The activity was not significantly related to age or gender. The AGT activity was similar in the Caucasian (7.1 ± 3.6 fmol/µg DNA, n = 42) and Japanese (8.9 ± 4.4 fmol/µg DNA, n = 14) groups. The overall range of activity was similar to that which we have reported previously in peripheral blood mononuclear cell AGT for >13 years in >300 samples (9 , 19, 20, 21, 22) and is the same range of peripheral blood mononuclear cell AGT activity seen in over 130 additional patient and normal donor samples analyzed in our laboratory that remain unreported. In none of these samples have we observed AGT of <1.5 or >32 fmol/µg DNA. Most importantly, we have never observed a human mononuclear sample with no AGT activity (limit of detection, 0.05 fmol/µg DNA, corresponding to ~180 molecules/cell). As we have reported previously, AGT measurement on the basis of cellular DNA is preferred because it allows better comparison to other tissues that have different relative amounts of DNA and protein (19) , and because in peripheral blood mononuclear cell preparations, red cell contamination may sometimes increase the amount of apparent protein that is not derived from mononuclear cells. Because red cells contain negligible amounts of AGT, this can lead to a falsely low estimate of AGT. Although we have data (which is available) for all samples in units of activity/mg cellular protein, we will not report it here.

To measure BG inhibition of AGT activity, an amount of cellular extract representing a fixed amount of enzyme activity, as determined by baseline enzyme assay, was incubated with BG in a concentration range of 0, 0.05, 0.2, 0.5, 1, 2, and 4 µM before adding [methyl-3H]calf thymus DNA. The amount of cellular protein used was 50 fmol (0, 0.05, and 0.2 µM BG) or 200 fmol (0.5, 1, 2, and 4 µM BG) of activity, depending upon the concentration of BG used. One BG stock solution in DMSO was used for all reaction concentrations, keeping final DMSO concentrations to 1% or less in the reactions. The reaction was preincubated for 30 min at 37°C, after which residual AGT activity was determined by adding [methyl-3H]calf thymus DNA substrate. AGT inactivation at each concentration was determined as the percentage of baseline activity. ED50 and ED90 values were obtained for each donor sample. AGT depletion by 30 min exposure to BG of extracts of these blood mononuclear cells was consistent in all samples. Fig. 1ACitation indicates that a similar pattern of AGT inactivation was observed in samples from Caucasian and Japanese groups. As shown in Table 1Citation , the mean ED50 for BG in the Caucasian donors was 0.37 ± 0.09 µM, n = 42, and among Japanese donors was 0.36 ± 0.11 µM, n = 14. Mean ED90 for BG in the Caucasian donors was lower, 1.06 ± 0.29 µM, n = 42, than in Japanese donors, 1.52 ± 0.51 µM, n = 14, P = 0.002. The distribution of ED50s is shown in Fig. 1BCitation and is independent of baseline AGT. Similar data were obtained for the ED90s. No outliers were evident, and all have ED50s were <0.8 µM BG.



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  		Fig. 1. Inactivation of human blood mononuclear cell AGT by O6-benzylguanine. A, blood mononuclear cell extract was treated with increasing concentrations of BG for 30 min before the addition of [methyl-3H]DNA substrate containing O6-mg. Residual AGT was determined and plotted against the concentration of BG. The mean inactivation curves are shown for Caucasian and Japanese donors. The means for Caucasian and Japanese donors are shown; bars, SD. B, the distribution of ED50s for BG inactivation are plotted relative to the baseline AGT activity for each donor. {blacksquare}, Caucasian donors; {diamondsuit}, Japanese donors.

 

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  		Table 1 Baseline AGT, ED50, and ED90 values between Caucasian and Japanese lymphocyte donors

 
To estimate the situation in which a donor mononuclear cell preparation expressed AGT from two different alleles, both wild-type AGT protein and AGT gly160arg protein carrying the Japanese polymorphism at position 160, we mixed either wild-type purified protein or an activity-equivalent amount of human mononuclear cell extract with purified Escherichia coli transformant-derived AGT gly160arg protein (17) . The aliquots of equal activity of AGTs (50 fmol activity for the purified wild-type or gly160arg mutant AGT, or a mixture of 25 fmol of wild-type with 25 fmol of gly160arg or mononuclear cell extracts) were pre-incubated with different concentrations of BG at 37°C for 30 min in assay buffer containing 50 µg of calf thymus DNA. The residual AGT activity was determined by incubating the samples with [3H] methylated DNA for 30 min at 37°C. The ED50s reflected the presence of the BG-sensitive wild-type protein (ED50, 1.3 µM) and the BG-resistant gly160arg AGT (ED50, 24 µM). In the mixture of purified proteins, the ED50 was 17 µM. For the mixture containing mononuclear cell extract and wild-type purified AGT, the ED90 was 1.8 µM, and with BG-resistant mutant AGT, the ED50 was 9 µM. These values were much higher than the ED50 and ED90 values we observed in any of the donor samples, indicating that there was no sample with a high degree of BG resistance.


   DISCUSSION
Top
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
REFERENCES
 
This study indicates that inactivation of AGT by BG is very uniform in a sample of 56 normal donors in the United States, including 42 Caucasians and 14 Japanese. No outliers with increased sensitivity or resistance to BG were seen, and there was no correlation between baseline AGT and BG inactivation in individual donors. These studies were undertaken because of a number of reports about the presence of polymorphisms in AGT, which could render the protein resistant to BG. Such polymorphisms, if prevalent in the population, could impact on the therapeutic efficacy of BG. Imai (16) reported that a polymorphism at position Gly160Arg was present in 10–15% of the Japanese population. Edara et al. (17) and Dolan (23) reported recently that this mutation renders the human AGT 20-fold resistant to inactivation of BG and its active metabolite, 8-oxobenzoguanine, suggesting that 15% of the Japanese population might be clinically resistant to BG. However, in a recent publication, Dolan (28) failed to find the gly160arg mutation in >200 DNA samples from American patients (95% confidence interval, 0–1.6%). Nonetheless, if the gly160arg mutation is present in human tumors, the two active compounds present in the plasma after BG exposure, using doses used in current clinical trials of between 80 and 120 mg/m2 (8 , 9) , would not be effective.

More recently, other AGT polymorphisms have been reported. These include Ile143Val, Lys178Arg (24) ; Leu84Phe and Trp65Cys (25) ; and other isolated mutations in cancer patients (26) . Whether these result in a BG-resistant AGT remains to be determined. On the other hand, some of the described MGMT mutants produce an AGT protein, which have less activity against O6-mG yet are BG resistant, suggesting that some of the possible mutation sites may be selected against because they have less ability to protect against naturally occurring O6-mG DNA adducts.

The tact we took, analysis of BG sensitivity, is quite different than a search for polymorphisms in the MGMT gene. We wanted to determine whether there was a functional difference in AGT among individuals, i.e., whether we could detect differences in AGT based on analysis of AGT activity in lymphocytes. From this we would infer that these BG-resistant AGT reflected germ-line mutations in the MGMT gene. We observed no such functional polymorphism among 56 donors and conclude that ED50 values of >1 µM BG are uncommon (95% confidence interval, 0–6%).

A final issue that remains in the assessment of altered AGT sensitivity to BG is whether AGT mutations that are BG resistant are present in patient tumors, although they may not be germ line. These could arise either during the transformation process, perhaps due to genomic instability, or be acquired during drug treatment. We have reported in preliminary form the acquisition of resistance to BG and BCNU in MCF-7 breast cancer cells (27) and colon cancer HCT116 cells (28) after repeated exposure to these agents. The MCF-7 cells resistant to BG and BCNU have normal AGT activity and normal AGT sensitivity to BG, suggesting that in these cells, resistance is not due to an alteration in AGT. In HCT116, however, data suggest that the cell has a mutated AGT with less reactivity toward O6-mG and markedly increased resistance to BG.4 This suggests that tumors might acquire resistance to BG and BCNU through mutation in the MGMT gene. Whether this occurs clinically and is responsible for acquired resistance to BG and BCNU remains to be evaluated.


   FOOTNOTES
 
The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

1 This work was supported in part by USPHS Grants U19-NCDDG-CA57725, P30CA43703, and RO1CA73062. Back

2 To whom requests for reprints should be addressed, at Division of Hematology/Oncology, Case Western Reserve University, BRB-3W, 10900 Euclid Avenue, Cleveland, OH 44106-4937. Phone: (216) 368-1176; Fax: (216) 368-1166; E-mail: slg5{at}po.cwru.edu Back

3 The abbreviations used are: AGT, O6-alkylguanine DNA-alkyltransferase; BCNU, 1,3-bis(2-chloroethyl)-1-nitrosourea; O6-mg, O6-methylguanine; MGMT, methylguanine DNA-methyltransferase; BG, O6-benzylguanine. Back

4 L. Liu et al., unpublished results. Back

Received 8/24/98; revised 12/29/98; accepted 12/31/98.


   REFERENCES
Top
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 

  1. Gerson S. L., Willson J. K. O6-Alkylguanine-DNA alkyltransferase. A target for the modulation of drug resistance. Hematol. Oncol. Clin. N. Am., 9: 431-50, 1995.[Medline]
  2. Yarosh D. B., Hurst-Calderone S., Babich M. A., Day R., III Inactivation of O6-methylguanine-DNA methyltransferase and sensitization of human tumor cells to killing by chloroethylnitrosourea by O6-methylguanine as a free base. Cancer Res., 46: 1663-1668, 1986.[Abstract/Free Full Text]
  3. Gerson S. L., Trey J. E. Modulation of nitrosourea resistance in myeloid leukemias. Blood, 71: 1487-1494, 1988.[Abstract/Free Full Text]
  4. Dumenco L. L., Allay E., Norton K., Gerson S. L. The prevention of thymic lymphomas in transgenic mice by human O6-alkylguanine-DNA alkyltransferase. Science (Washington DC), 259: 219-222, 1993.[Abstract/Free Full Text]
  5. Day R. S. I., Ziolkowski C. H. J., Scudiero D. A., Meyer S. A., Mattern M. R. Human tumor cell strains defective in the repair of alkylation damage. Carcinogenesis (Lond.), 1: 21-32, 1980.[Abstract/Free Full Text]
  6. Dolan M. E., Moschel R. C., Pegg A. E. Depletion of mammalian O6-alkylguanine-DNA alkyltransferase activity by O6-benzylguanine provides a means to evaluate the role of this protein in protection against carcinogenic and therapeutic alkylating agents. Proc. Natl. Acad. Sci. USA, 87: 5368-5372, 1990.[Abstract/Free Full Text]
  7. Gerson S., Zborowska E., Norton K., Gordon N., Willson J. Synergistic efficacy of O6-benzylguanine and BCNU in human colon cancer xenografts completely resistant to BCNU alone. Biochem. Pharmacol., 46: 483-491, 1993.[Medline]
  8. Dolan M., Roy S., Fasanmade A., Paras P., Shilsky R., Ratain M. O6-Benzylguanine in man: metabolic, pharmacokinetic and pharmacodynamic findings. J. Clin. Oncol., 16: 1803-1809, 1998.[Abstract]
  9. Spiro T., Gerson S. L., Hoppel C. L., Liu L., Schupp J., Majka S., Haaga J., Willson J. K.V. O6-Benzylguanine totally depletes alkylguanine-DNA alkyltransferase in tumor tissue: a phase I pharmacokinetic/pharmacodynamic study. Proc. Am. Soc. Clin. Oncol., 17: 212a 1998.
  10. Pegg A. E., Boosalis M., Samson L., Moschel R. C., Byers T. L., Swenn K., Dolan M. E. Mechanism of inactivation of human O6-alkylguanine-DNA alkyltransferase by O6-benzylguanine. Biochemistry, 32: 11998-2006, 1993.[Medline]
  11. Tano K., Shiota S., Collier J., Foote R. S., Mitra S. Isolation and structural characterization of a cDNA clone encoding the human DNA repair protein for O6-alkylguanine. Proc. Natl. Acad. Sci. USA, 87: 686-690, 1990.[Abstract/Free Full Text]
  12. Dolan M. E., Pegg A. E., Dumenco L. L., Moschel R. C., Gerson S. L. Comparison of the inactivation of mammalian and bacterial O6-alkylguanine-DNA alkyltransferases by O6-benzylguanine and O6-methylguanine. Carcinogenesis (Lond.), 12: 2305-2309, 1991.[Abstract/Free Full Text]
  13. Encell L. P., Coates M. M., Loeb L. A. Engineering human DNA alkyltransferases for gene therapy using random sequence mutagenesis. Cancer Res., 58: 1013-1020, 1998.[Abstract/Free Full Text]
  14. Crone T. M., Pegg A. E. A single amino acid change in human O6-alkylguanine-DNA alkyltransferase decreasing sensitivity to inactivation by O6-benzylguanine. Cancer Res., 53: 4750-4753, 1993.[Abstract/Free Full Text]
  15. Goodtzova K., Kanugula S., Edara S., Pauly G. T., Moschel R. C., Pegg A. E. Repair of O6-benzylguanine by the Escherichia coli Ada and Ogt and the human O6-alkylguanine-DNA alkyltransferases. J. Biol. Chem., 272: 8332-8339, 1997.[Abstract/Free Full Text]
  16. Imai Y., Oda H., Nakatsuru Y., Ishikawa T. A polymorphism at codon 160 of human O6-methylguanine-DNA methyltransferase gene in young patients with adult type cancers and functional assay. Carcinogenesis (Lond.), 16: 2441-2445, 1995.[Abstract/Free Full Text]
  17. Edara S., Kanugula S., Goodtzova K., Pegg A. E. Resistance of the human O6-alkylguanine-DNA alkyltransferase containing arginine at codon 160 to inactivation by O6-benzylguanine. Cancer Res., 56: 5571-5575, 1996.[Abstract/Free Full Text]
  18. Gerson S. L., Miller K., Berger N. A. O6-Alkylguanine-DNA alkyltransferase activity in human myeloid cells. J. Clin. Invest., 76: 2106-2114, 1985.
  19. Gerson S. L., Trey J. E., Miller K., Berger N. A. Comparison of O6-alkylguanine-DNA alkyltransferase activity based on cellular DNA content in human, rat and mouse tissues. Carcinogenesis (Lond.), 7: 745-749, 1986.[Abstract/Free Full Text]
  20. Gerson S. L. Modulation of human lymphocyte O6-alkylguanine-DNA alkyltransferase by streptozotocin in vivo. Cancer Res., 49: 3134-3138, 1989.[Abstract/Free Full Text]
  21. Gerson S. L., Phillips W., Kastan M., Dumenco L., Donovan C. Human CD34 hematopoietic progenitors have low, cytokine-unresponsive O6-alkylguanine-DNA alkyltransferase and are sensitive to O6-benzylguanine plus BCNU. Blood, 88: 1649-1655, 1996.[Abstract/Free Full Text]
  22. Gerson S. L., Spiro T., Reidenberg P. Rapid depletion of O6-alkylguanine DNA alkyltransferase with twice daily oral temozolomide (SCH 52365) in patients with advanced cancer. Proc. Am. Soc. Clin. Oncol., 15: 178 1996.
  23. Wu M. H., Lohrbach K. E., Olopade O. I., Kokkinakis D. M., Friedman H. S., Dolan M. E. Lack of evidence for a polymorphism at codon 160 of human O6-alkylguanine-DNA alkyltransferase gene in normal tissue and cancer. Clin. Cancer Res., 5: 209-213, 1999.[Abstract/Free Full Text]
  24. Deng C., Xie D., Zhao Y., Wang L., Hong J. Identification of a novel genetic polymorphism of human O6-alkylguanine-DNA alkyltransferase. Proc. Am. Assoc. Cancer Res., 39: 455 1998.
  25. Otsuka M., Abe M., Nakabeppu Y., Sekiguchi M., Suzuki T. Polymorphism in the human O6-methylguanine-DNA methyltransferase gene detected by PCR-SSCP analysis. Pharmacogenetics, 6: 361-363, 1996.[Medline]
  26. Wang L., Zhu D., Zhang C., Mao X., Wang G., Mitra S., Li B. F., Wang X., Wu M. Mutations of O6-methylguanine-DNA methyltransferase gene in esophageal cancer tissues from Northern China. Int. J. Cancer, 71: 719-723, 1997.[Medline]
  27. Phillips W., Gerson S. L. Acquired resistance to O6-benzylguanine and BCNU in MCF-7. Proc. Am. Assoc. Cancer Res., 37: 333 1996.
  28. Liu L., Phillips W. J., Gerson S. L. Resistance to O6bG+BCNU is mediated by either AGT dependent or independent mechanisms in human colon cancer cells. Proc. Am. Assoc. Cancer Res., 38: 522 1997.



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